Theory Value

(*  Title:      HOL/MicroJava/J/Value.thy
    ID:         $Id: Value.thy,v 1.12 2007/09/30 19:55:17 wenzelm Exp $
    Author:     David von Oheimb
    Copyright   1999 Technische Universitaet Muenchen
*)

header {* \isaheader{Java Values} *}

theory Value imports Type begin

-- " typedecl loc'  locations, i.e. abstract references on objects " 

types loc' = nat -- "locations, i.e. abstract references on objects"

datatype loc 
  = XcptRef xcpt -- "special locations for pre-allocated system exceptions"
  | Loc loc'     -- "usual locations (references on objects)"

datatype val
  = Unit        -- "dummy result value of void methods"
  | Null        -- "null reference"
  | Bool bool   -- "Boolean value"
  | Intg int    -- "integer value, name Intg instead of Int because
                   of clash with HOL/Set.thy" 
  | Addr loc    -- "addresses, i.e. locations of objects "
  | RetAddr nat -- "return address of JSR instruction, for bytecode only"

consts
  the_Bool :: "val => bool"
  the_Intg :: "val => int"
  the_Addr :: "val => loc"
  the_RetAddr :: "val => nat"

primrec
  "the_Bool (Bool b) = b"

primrec
  "the_Intg (Intg i) = i"

primrec
  "the_Addr (Addr a) = a"

primrec
  "the_RetAddr (RetAddr r) = r"


consts
  defpval :: "prim_ty => val"  -- "default value for primitive types"
  default_val :: "ty => val"   -- "default value for all types"

primrec
  "defpval Void    = Unit"
  "defpval Boolean = Bool False"
  "defpval Integer = Intg 0"
  "defpval (RetA pc) = RetAddr pc"

primrec
  "default_val (PrimT pt) = defpval pt"
  "default_val (RefT  r ) = Null"

end